Fastify 5.3.0 release notes

fix: wrong reply return type by @dangkyokhoang in https://github.com/fastify/fastify/pull/6026
feat: allow to access decorators by @jean-michelet in https://github.com/fastify/fastify/pull/5768
ci: continue-on-error on alternative runtime by @Eomm in https://github.com/fastify/fastify/pull/6031
fix: clear [kState].readyPromise for garbage collection by @LiviaMedeiros in https://github.com/fastify/fastify/pull/6030
ci: set workflow permissions to read-only by default by @Fdawgs in https://github.com/fastify/fastify/pull/6035
chore: Bump the dependencies-major group with 2 updates by @dependabot in https://github.com/fastify/fastify/pull/6036
chore: Bump lycheeverse/lychee-action from 2.3.0 to 2.4.0 by @dependabot in https://github.com/fastify/fastify/pull/6037
chore: remove sponsort by @Eomm in https://github.com/fastify/fastify/pull/6040
test: fix skip in upgrade test by @LiviaMedeiros in https://github.com/fastify/fastify/pull/6044
chore: migrate custom-parser.4.test.js to node:test by @Matthew-Mallimo in https://github.com/fastify/fastify/pull/6042
docs: add fastify-lm to Ecosystem.md by @galiprandi in https://github.com/fastify/fastify/pull/6032
test: skip IPv6 tests if its support is not present by @LiviaMedeiros in https://github.com/fastify/fastify/pull/6048

Full Changelog: https://github.com/fastify/fastify/compare/v5.2.2...v5.3.0